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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: akpm@linux-foundation.org, arunks@codeaurora.org, brgl@bgdev.pl,
	geert+renesas@glider.be, ldufour@linux.ibm.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	mguzik@redhat.com, mhocko@kernel.org, rppt@linux.ibm.com,
	vbabka@suse.cz, ktkhai@virtuozzo.com
Subject: Re: [PATCH v3 2/2] prctl_set_mm: downgrade mmap_sem to read lock
Date: Thu, 2 May 2019 23:57:34 +0300	[thread overview]
Message-ID: <20190502205734.GE2488@uranus.lan> (raw)
In-Reply-To: <20190502125203.24014-3-mkoutny@suse.com>

On Thu, May 02, 2019 at 02:52:03PM +0200, Michal Koutný wrote:
> The commit a3b609ef9f8b ("proc read mm's {arg,env}_{start,end} with mmap
> semaphore taken.") added synchronization of reading argument/environment
> boundaries under mmap_sem. Later commit 88aa7cc688d4 ("mm: introduce
> arg_lock to protect arg_start|end and env_start|end in mm_struct")
> avoided the coarse use of mmap_sem in similar situations. But there
> still remained two places that (mis)use mmap_sem.
> 
> get_cmdline should also use arg_lock instead of mmap_sem when it reads the
> boundaries.
> 
> The second place that should use arg_lock is in prctl_set_mm. By
> protecting the boundaries fields with the arg_lock, we can downgrade
> mmap_sem to reader lock (analogous to what we already do in
> prctl_set_mm_map).
> 
> v2: call find_vma without arg_lock held
> v3: squashed get_cmdline arg_lock patch
> 
> Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct")
> Cc: Yang Shi <yang.shi@linux.alibaba.com>
> Cc: Mateusz Guzik <mguzik@redhat.com>
> CC: Cyrill Gorcunov <gorcunov@gmail.com>
> Co-developed-by: Laurent Dufour <ldufour@linux.ibm.com>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>

  reply	other threads:[~2019-05-02 20:57 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-17 12:03 [PATCH] mm: get_cmdline use arg_lock instead of mmap_sem Michal Koutný
2019-04-17 13:41 ` Michal Hocko
2019-04-17 14:41   ` Michal Koutný
2019-04-17 14:55     ` Michal Hocko
2019-04-18 13:50       ` [PATCH] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-04-18 14:09         ` Cyrill Gorcunov
2019-04-18 14:15         ` Michal Hocko
2019-04-18 14:27         ` Laurent Dufour
2019-04-18 18:23         ` Cyrill Gorcunov
2019-04-30  8:18           ` [PATCH 0/3] Reduce mmap_sem usage for args manipulation Michal Koutný
2019-04-30  8:18             ` [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem Michal Koutný
2019-04-30  9:09               ` Kirill Tkhai
2019-04-30  9:38                 ` Cyrill Gorcunov
2019-04-30  9:53                   ` Kirill Tkhai
2019-04-30 10:45                     ` Cyrill Gorcunov
2019-04-30 10:56                       ` Michal Koutný
2019-04-30 13:24                         ` Cyrill Gorcunov
2019-04-30  8:18             ` [PATCH 2/3] prctl_set_mm: Refactor checks from validate_prctl_map Michal Koutný
2019-04-30  9:27               ` Kirill Tkhai
2019-04-30  8:18             ` [PATCH 3/3] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-04-30  8:55               ` Kirill Tkhai
2019-04-30  9:08                 ` Cyrill Gorcunov
2019-04-30  9:11                   ` Kirill Tkhai
2019-05-02 12:52                     ` [PATCH v3 0/2] Reduce mmap_sem usage for args manipulation Michal Koutný
2019-05-02 12:52                       ` [PATCH v3 1/2] prctl_set_mm: Refactor checks from validate_prctl_map Michal Koutný
2019-05-02 20:57                         ` Cyrill Gorcunov
2019-05-02 12:52                       ` [PATCH v3 2/2] prctl_set_mm: downgrade mmap_sem to read lock Michal Koutný
2019-05-02 20:57                         ` Cyrill Gorcunov [this message]
2019-05-06  9:28                         ` Kirill Tkhai
2019-05-07 17:42                         ` Michal Hocko

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